What is the difference between betadine and povidone iodine

5.1 Polyvinylpyrrolidone–Iodine

Polyvinylpyrrolidone–iodine (PVP-I) disinfection varies on concentration and duration depending on the ability of the chorion to withstand exposure. PVP-I can be purchased as a solid powder or as a dilute liquid (also known as povidine–iodine). PVP-I stock solutions should be maintained at 10% or higher in a dark container, and dilutions of PVP-I should be made the day of germfree egg derivation in a fish-safe medium and filter sterilized. Due to possible lot-to-lot variability, several concentrations within fourfold dilutions of the established protocols should be tested when using commercially obtained diluted liquid PVP-I to determine the appropriate concentration to sterilize eggs while maintaining fish viability. Because of the instability of the chemical, dilute liquid PVP-I should not be used in a gnotobiotic protocol more than 6 months after opening, and very dilute (less than 10%) PVP-I solutions should be not be used more than a day after dilution.

For some fish, such as zebrafish, the concentration of PVP-I is very low (0.1%), whereas for other fish, such as stickleback, the concentration may be up to four times higher. Similarly, the strength of the chorion will determine how long an egg may soak in PVP-I. For example, zebrafish can only withstand a 2-min soak in 0.1% PVP-I, whereas stickleback can be exposed to 0.4% PVP-I for up to 8 min without long-term effects on survival or development. Prolonged exposure to PVP-I may inhibit the development of fish. Therefore, fish should be rinsed several times with sterile fish medium following a soak in PVP-I.

Povidone-Iodine

Povidone-iodine (Betadine) is a complex of the potent bactericidal agent iodine and the carrier molecule povidone. On contact with tissues, the carrier complex slowly releases free iodine. Gradual release decreases tissue irritation and reduces potential toxicity while preserving the agent’s germicidal activity. Povidone-iodine is effective against gram-positive and gram-negative bacteria, fungi, and viruses.8 In contrast to chlorhexidine, povidone-iodine has a shorter protective effect against bacterial buildup on the skin after hand washing and seems to be less effective than these agents for that purpose.9

Povidone-iodine is manufactured as a solution by itself (povidone-iodine solution) or in conjunction with an ionic detergent (povidone-iodine scrub preparation). The detergent in the scrub preparation seems to be toxic to several normal tissues and to components of an open wound.1,10 Excessive exposure of open wounds to scrub solutions by wound scrubbing or soaking is not recommended. Scrub solutions were designed for preoperative preparation of intact skin before operative incisions.

Povidone-iodine, without the detergent, is distributed most commonly as a 10% solution. When diluted to a 1% concentration or lower, it can be applied safely to wounds, and it retains its bactericidal activity.11 It has no inherent negative effect on wound healing.12 The lack of clinical toxicity of povidone-iodine without detergent was shown with 225 patients undergoing ophthalmologic surgery.13 Povidone-iodine 10% solution, diluted with saline, was used to prepare the eye and its surrounding structures for surgery. There was no reported corneal, conjunctival, or skin toxicity. Adverse and allergic reactions are extremely rare, even when the solution is used in known iodine-allergic patients.14

Observational studies

Povidone–iodine solution has been used as an effective broad-spectrum antiseptic and disinfectant since the 1950s. In the early 1980s, a tumoricidal effect was reported. In colorectal operations, povidone–iodine has generally been used for the purpose of minimizing postoperative septic complications and reducing cancer recurrence, although there is little evidence to support its use.

In a review of the literature on the use of povidone–iodine in colorectal surgery, few prospective randomized controlled trials were identified (20R). The authors found no conclusive evidence of benefits but were able to comment on adverse effects. Serious adverse effects of povidone–iodine were not common; metabolic acidosis, acute renal failure, hyperthyroidism and toxic reactions to iodine or iodide had been reported. The authors recommended that in general povidone–iodine should be avoided in patients with a history of allergic reactions to iodine-containing compounds, thyroid disease, renal insufficiency and established systemic sepsis.

Wounds

Povidone iodine inhibits leukocyte migration and fibroblast aggregation in wounds. The effect on the wound healing process has been studied in 294 children undergoing surgery, 283 of whom had undergone appendectomy [6]. In a first series using 5% povidone iodine aerosol for preoperative disinfection, the postoperative wound infection rate was 19% in the test group and only 8% in the controls. When a 1% povidone iodine solution was used, only 2.6% of the patients were infected (control group 8.5%). Using a drain with a cellulose viscose sponge, 5% povidone iodine by aerosol inhibited leukocyte migration, but no cell aggregates or fibroblasts were detected. A 5% solution allowed better cellular movement and attachment to the framework, polymorphonuclear leukocytes predominating. The excipients in the aerosol formula must be more toxic to the cell than those in the solution. If a 1% povidone iodine solution was absorbed by the sponge, the aggregation phenomenon was only slightly averted and cell morphology was similar to that of the saline control.

Povidone iodine reduced the number of wound infections only in patients with appendicitis in whom neither peritonitis nor a periappendicular abscess had yet developed [7].

Povidone-Iodine

Povidone-iodine is an antimicrobial agent active against Gram-positive and Gram-negative bacteria. It is commonly used as an antiseptic perioperatively and for skin wounds.310 Surgery involving the feet is complicated by high rates of infection, and the addition of 70% isopropyl alcohol to 7.5% to 10% povidone-iodine was more effective than 4% chlorhexidine in reducing the bacterial load from the first web space of normal feet.311

The incidence of ACD is rare.312 However, irritant contact dermatitis with tissue necrosis has resulted from prolonged contact with large quantities of povidone-iodine.310 Cases of irritant contact dermatitis resembling vasculitis313 and toxic epidermal necrolysis314 have also been reported. The recent FDA ruling discussed above also listed povidone-iodine as one of six ingredients that would require further study to address efficacy and safety in healthcare.300

4.5 Stability of the Complex

Povidone-iodine can be stored as a solid-state powder without significant loss of iodine. Samples stored at 65°C in glass-stoppered bottles for as long as three years showed only 0.5% loss of available iodine. Because povidone-iodine exhibits only negligible vapor pressure (0.01 torr as compared to 3.3 torr for elemental iodine at 56°C), the iodine does not sublime even at elevated temperatures. However, the material is hygroscopic and should be protected from moisture [8].

The stability of povidone-iodine solutions is much higher than that of iodine tincture or of Lugol's solution. Aqueous solutions of the complex containing 2% available iodine were found to remain unchanged when stored for one year at room temperature. Experimental data relating the relative loss of available iodine from povidone-iodine solutions and other iodine preparations are given in Table 3.

Table 3. Percent Iodine Remaining After Storage of Various Iodine Preparations

Note: In the open beaker studies, the solution volume was maintained at a constant level through the addition of solvent.

PVP-I and thyroid dysfunction

PVP-I is used frequently in various fields as a broad-spectrum topical disinfectant for bacteria, funguses, viruses and protozoa. It is a powder containing 10% iodine (Figures 96.1 and 96.2). The available iodine content in the preparation varies from 0.05 to 1%. PVP-I solutions used for disinfection of the skin or wounds have a 1% iodine content.

Little iodine is absorbed by healthy skin in a short period (Moody et al., 1988), so there is no concern about potential absorption of iodine after washing the hands with PVP-I (Nobukuni and Kawahara, 2002). However, iodine absorption from sites of topical treatment with PVP-I is enhanced if it is applied to injured skin or mucosal surfaces, or even to extensive areas of intact skin (Dela Cruz et al., 1987). High permeability of the skin of neonates allows the absorption of large amounts of iodine.

Vaginal douching with PVP-I by women can cause transient hypothyroidism in their neonates and increased the false-positive rate of screening for congenital hypothyroidism in an iodine-deficient region of Germany (Grüters et al., 1983), and even in iodine-sufficient areas of Japan (Koga et al., 1995). It has been suggested that iodine-rich breast milk may play an important role in this increased recall rate (Chanoine et al., 1988; Koga et al., 1995).

Iodine is readily absorbed when PVP-I is applied to the skin of a newborn infant, because of high cutaneous permeability, and neonates are very sensitive to iodine overload, as described previously. Topical PVP-I therapy is associated with a significant risk of hypothyroidism in neonates, especially very-low-weight babies (Smerdely et al., 1989). Many cases of hypothyroidism induced by topical use of PVP-I have been reported in newborn infants, mainly from iodine-deficient regions (Markou et al., 2001). However, a case of severe hypothyroidism in a neonate was also reported from North America, an iodine-sufficient region (Khashu et al. 2005). A premature infant developed severe hypothyroidism that required l-thyroxine replacement therapy after application of PVP-I for 20 days.

The serum iodine concentration is extremely elevated in patients who have severe burns and are treated with PVP-I. Rath et al. (1988) reported two cases of hyperthyroidism in burn patients. Both patients had no history of thyroid disease and follow-up examination after recovery from injury revealed normal thyroid function. After topical treatment with PVP-I was discontinued, the thyroid function of these patients returned to normal within a few weeks. In one patient, PVP-I treatment was repeated and this led to hyperthyroidism, which was also readily reversible.

There have been many reports of a decrease in thyroxine (T4) and triiodothyronine (T3), as well as an increase in TSH, in burns patients receiving PVP-I treatment. However, these changes in thyroid hormones may represent part of general stress response (Becker et al., 1980).

Iodine is readily absorbed from mucosal surfaces. Peritoneal lavage with PVP-I was reported to frequently induce transient thyroid dysfunction in patients from Germany where dietary iodine ingestion is relatively low (Gortz et al., 1984). In Japan (an iodine-sufficient region), however, intraoperative bowel irrigation with PVP-I does not cause thyroid dysfunction (Tsunoda et al., 2000).

Long-term treatment with PVP-I, even at a relatively low dose, can result in thyroid dysfunction. Out of 27 patients in whom PVP-I was applied on the tracheotomy site, the gastrostomy site, the external urethral meatus, or an ulcerated skin for 3–133 months (mean±standard deviation 48.0±33.2), subclinical hypothyroidism was seen in 3 patients, mild hyperthyroidism was seen in 1 patient, and subclinical hyperthyroidism was suspected in 7 patients (Nobukuni et al., 1997). Sato et al. (2007) reported two cases of hypothyroidism induced by prolonged habitual gargling with PVP-I for 4 and 10 years, respectively. Shetty and Duthie (1990) and Valayer-Chaleat et al. (1998) reported cases of hyperthyroidism in patients who received topical application of PVP-I for 6 months to treat decubitus ulcers.

Agents Commonly Used for Operative Site Skin Preparation and Surgical Hand Washing

Povidone-iodine or iodophor products are supplied in two distinct liquid versions. For the operative site preparation, a detergent scrub is first applied with sponges to mechanically remove gross dirt and oils from the skin. After the skin has been blotted with a sterile towel, a nondetergent solution is “painted” onto the area. This thin film of povidone-iodine continues to have bactericidal action for up to 8 hours after application. The solution's brown color also effectively outlines the borders of the surgical scrub, allowing accurate placement of the towels and drapes before incision. Patients and OR staff who have a history of sensitivity or allergic reaction to iodine should refrain from the use of either of these preparations for surgical scrubs.

Chlorhexidine gluconate, when used in a 4% concentration, is bactericidal and has persistent antimicrobial activity after application. Repeated scrubbing throughout the day enhances its activity. Because this agent is nonirritating for a majority of the patient population, it is commonly used for hand washing and preparation of the operative site. Chlorhexidine gluconate scrub soap adequately prepares the skin, and no solution is required after the scrub.

Parachlorometaxylenol (PCMX) is a useful skin preparation agent, particularly for those allergic to iodine-containing preparations. This agent is often combined with an emollient to reduce skin drying.

Hexachlorophene, although used infrequently, is an effective skin preparation solution for those patients and staff allergic to povidone-iodine and chlorhexidine gluconate. It accumulates on the skin after several days of use, causing an overall decrease in skin flora.

OTHER ANTIFUNGALS

4.12.9 Vaginal therapeutics

Povidone iodide as vaginal suppositories and iodine rinses of the vagina are problematic due to the enrichment of free iodides in the mother’s milk with potential effects on the child’s thyroid function (Chapter 4.11).

There is no reason to wean treatment with other vaginal therapeutics, containing disinfectants, i.e. dequalinium chloride salts, hexetidine, policresulen or estrogens. However, a rationale for treatment with a particular drug is desired, avoiding drugs that are controversial with respect to their effectiveness. Anti-infective therapy, i.e. with metronidazole for trichomoniasis or with the nitrofurantoin nifuratel as well as the antimycotic, chlorphenesin should be critically considered. In the case of a proven bacterial infection, a systemic (oral) therapy should be considered, which, in general, is also compatible with breastfeeding – and more effective.

Vaginally used spermicidal contraceptives such as nonoxinol are no problem for the breastfed child, likewise the use of different intrauterine devices (IUD).